1. Field of the Invention
This invention relates to a method of processing legumina or soybeans. More specifically, the invention is concerned with a method of deodorizing or eliminating any offensive smell fully from raw soybeans so as to be rendered palatable.
2. Description of the Prior Art
A soybean crop, because of its abundance in proteins, has been widely grown throughout the world for human consumption as a good supply source of vegetable proteins. Principal of these soybean proteins are globulins and albumins, above all, glycinin generally classified as a globulin. The globulins and albumins are composed of essential amino acids such as lysine, leucine, isoleucine, arginine, histidine, phenylalanine, tryptophan, valine and the like, as well as about ten nonessential amino acids. These essential amino acids are so balanced in the soybean proteins as to be suitable for human nutrition.
It has been found that the soybean proteins contain 4 to 17 times as much essential amino acids as wheat proteins. Lysine is one of the amino acids that is extremely deficient in the wheat proteins. The soybean proteins have 16.6 times as much lysine as the wheat proteins. Furthermore, the soybean proteins have 8.1 times as much leucine and isoleucine, 7.1 times as much arginine, 5.3 times as much histidine, 8.5 times as much phenylalanine, 4.5 times tryptophan, and 12.9 times as much valine. Soybeans are therefore valuable as a supplement to wheat flour.
It has recently been accepted that the soybean proteins are even more nutritious than animal proteins. This has lent a great upsurge of soybeans being processable as food directly into the form of particulate, milky and paste products.
However, a disagreeable grassy-smell is peculiar to soybeans in the raw or green stage which cannot be used as such for edible purposes. This smell is known to be attributable to a protein enzyme or lipoxidase derived from some aldehydes and alcohols present in the beans. Several processes have heretofore been proposed to remove such a smell from the soybeans. One typical process involves treating green soybeans with certain alkaline chemicals, saturated steam or hot air. This known method has a drawback that the resulting beans do not smell unpleasant, but tend to be adversely affected even in their meat texture. For example, these bean meats when processed give milk products with large amounts of insoluble matter and in low yields.
Although water boiling may volatilize and remove from green soybeans any substances which would induce an unpleasant smell, the beans become substantially extracted with water. The boiled beans if dried give rise to a flavor or taste different totally from that of the green beans and can only be processed into limited foods such as bean paste (miso), bean curds (tofu), steamed and fermented beans (natto) and similar foods. These foods are usually inherent to the Orient.
Accordingly, no dietary varieties of soybean products are obtainable with the prior art processes.